 |
Datenblatt-Suchmaschine für elektronische Bauteile |
|
|
Datenblatt-Suchmaschine für elektronische Bauteile |
|
TC500COE Datenblatt(PDF) 6 Page - Microchip Technology |
|
||||||||||||||||||||||||||||||
TC500COE Datenblatt(HTML) 6 Page - Microchip Technology |
|
|
6 / 28 page  TC500/A/510/514 DS21428B-page 6 © 2002 Microchip Technology Inc. 3.0 DETAILED DESCRIPTION 3.1 Dual Slope Conversion Principles Actual data conversion is accomplished in two phases: input signal Integration and reference voltage De-integration. The integrator output is initialized to 0V prior to the start of Integration. During Integration, analog switch S1 connects VIN to the integrator input where it is main- tained for a fixed time period (TINT). The application of VIN causes the integrator output to depart 0V at a rate determined by the magnitude of VIN and a direction determined by the polarity of VIN. The De-integration phase is initiated immediately at the expiration of TINT. During De-integration, S1 connects a reference voltage (having a polarity opposite that of VIN) to the integrator input. At the same time, an external precision timer is started. The De-integration phase is maintained until the comparator output changes state, indicating the integrator has returned to its starting point of 0V. When this occurs, the precision timer is stopped. The De-inte- gration time period (TDEINT), as measured by the preci- sion timer, is directly proportional to the magnitude of the applied input voltage (see Figure 3-3). A simple mathematical equation relates the Input Sig- nal, Reference Voltage and Integration time: EQUATION 3-1: For a constant VIN: EQUATION 3-2: The dual slope converter accuracy is unrelated to the integrating resistor and capacitor values as long as they are stable during a measurement cycle. An inherent benefit is noise immunity. Input noise spikes are integrated (averaged to zero) during the integration periods. Integrating ADCs are immune to the large conversion errors that plague successive approximation converters in high noise environments. Integrating converters provide inherent noise rejection with at least a 20dB/decade attenuation rate. Interfer- ence signals with frequencies at integral multiples of the integration period are, theoretically, completely removed, since the average value of a sine wave of frequency (1/T) averaged over a period (T) is zero. Integrating converters often establish the integration period to reject 50/60Hz line frequency interference signals. The ability to reject such signals is shown by a normal mode rejection plot (Figure 3-1). Normal mode rejection is limited in practice to 50 to 65dB, since the line frequency can deviate by a few tenths of a percent (Figure 3-2). FIGURE 3-1: INTEGRATING CONVERTER NORMAL MODE REJECTION FIGURE 3-2: LINE FREQUENCY DEVIATION 1 RINTCINT VREFTDEINT RINTCINT TINT 0 VIN(T)DT = ∫ Where: VREF = Reference Voltage TINT = Signal Integration time (fixed) tDEINT = Reference Voltage Integration time (variable) VIN =VREF TDEINT TINT 30 20 10 0 0.1/T 1/T 10/T Input Frequency T = Measurment Period 0.01 0.1 1.0 80 70 60 50 40 30 20 t = 0.1 sec Line Frequency Deviation from 60 Hz (%) Normal Mode REJECTION = 20 LOG DEV = Deviation from 60Hz t = Integration Period SIN 60 t (1 ± ) p p DEV 100 DEV 100 60 t (1 ± ) |
Ähnliche Teilenummer - TC500COE |
|
Ähnliche Beschreibung - TC500COE |
|
|
Link URL |
| Privatsphäre und Datenschutz |
| ALLDATASHEETDE.COM |
| War ALLDATASHEET hilfreich? [ DONATE ] |
Über Alldatasheet | Werbung | Kontakt | Privatsphäre und Datenschutz | Linktausch | Hersteller All Rights Reserved©Alldatasheet.com |
| Russian : Alldatasheetru.com | Korean : Alldatasheet.co.kr | Spanish : Alldatasheet.es | French : Alldatasheet.fr | Italian : Alldatasheetit.com Portuguese : Alldatasheetpt.com | Polish : Alldatasheet.pl | Vietnamese : Alldatasheet.vn Indian : Alldatasheet.in | Mexican : Alldatasheet.com.mx | British : Alldatasheet.co.uk | New Zealand : Alldatasheet.co.nz |
|
Family Site : ic2ic.com |
icmetro.com |
German ▼
English
Chinese
German
Japanese
Russian
Korean
Spanish
French
Italian
Portuguese
Polish
Vietnamese
Indian
Mexican
British
New Zealand
